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| 2. |
- Biel, Anders, et al.
(författare)
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The use of MgO-paste as a biodegradeable bone cement
- 2016
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Ingår i: Materials Today. - : Elsevier. - 2214-7853. ; 3:2, s. 556-561
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Tidskriftsartikel (refereegranskat)abstract
- The use of MgO-paste as bone cement was tested on titanium cylinders implanted into rat tibia. The evaluation of bone healingwas made with the retention force (pull-out) test, light microscopy and ESEM/ EDX. Preimplantation of the MgO-paste into drillperforations of rat tibia increased the retention of the titanium implant 6-fold. The error was expressed as the 95% confidenceinterval of means (n=10 bones in each group). The observed difference between 3.46+/-0.71 N/mm2 for Ti-cylinders implantedwith MgO-paste and 0.56+/-0.26 N/mm2 for Ti-cylinders implanted directly into the bone, is statistically significant (p<0.01).The increase of retention force, caused by MgO is parallel to an increased thickness of the compact bone surrounding the implantand closer contact between bone and implant.Histological examination of the implant-related bone showed that the MgO-induced bone growth is mediated by the formation ofa bone-inducing matrix. The matrix contains organic substance, most likely proteins.
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| 3. |
- Gustafsson, Erik, et al.
(författare)
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Characterizing the dynamics of the quorum-sensing system in Staphylococcus aureus
- 2004
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Ingår i: Journal of molecular microbiology and biotechnology. - : S. Karger AG. - 1464-1801. ; 8:4, s. 232-242
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Tidskriftsartikel (refereegranskat)abstract
- The virulence determinants of <i>Staphylococcus aureus</i> are expressed in a growth phase-dependent manner governed by the autoinducible quorum-sensing system <i>agr</i>. Activation of the <i>agr</i> system results in a rapid increase in the regulator RNAIII and occurs in response to accumulation of AIP. In order to activate the <i>agr</i> system, a basal transcription of <i>agr</i> components must be assumed. This basal transcription of <i>agr</i> components seems to be stimulated by <i>sarA</i>. To better understand how SarA would affect activation of the <i>agr</i> system by modulating the basal <i>agr</i> activity, a mathematical model for autoactivation of the <i>agr</i> system was set up. The model predicted that the <i>agr</i> system is hysteretic, meaning that the <i>agr</i> system is activated at a specific concentration of autoinducing peptide (AIP), whereas it is inactivated at a specific lower concentration of AIP. According to the model, changing the basal <i>agr</i> activity only had a marginal effect on steady-state levels of RNAIII but changed the sensitivity of the cells to AIP. This was supported by Northern blot analysis of RNAIII in <i>S. aureus</i> mutants with different levels of SarA expression. Since natural antagonistic AIPs have been demonstrated, the effect of adding inhibitors to the system was analyzed.
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| 4. |
- Gustafsson, Erik, et al.
(författare)
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Mathematical modelling of the regulation of spa (protein A) transcription in Staphylococcus aureus.
- 2009
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Ingår i: International journal of medical microbiology : IJMM. - : Elsevier BV. - 1618-0607 .- 1438-4221. ; 299:1, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- In the present work a general systems biology approach has been used to study the complex regulatory network controlling the transcription of the spa gene, encoding protein A, a major surface protein and an important virulence factor of Staphylococcus aureus. A valid mathematical model could be formulated using parameter values, which were fitted to quantitative Northern blot data from various S. aureus regulatory mutants using a gradient search method. The model could correctly predict spa expression levels in 4 different regulatory mutants not included in the parameter value search, and in 2 other S. aureus strains, SH1000 and UAMS-1. The mathematical model revealed that sarA and sarS seem to balance each other in a way that when the activating impact of sarS is small, e.g. in the wild-type, the repressive impact of sarA is small, while in an agr-deficient background, when the impact of sarS is maximal, the repressive impact of sarA is close to its maximum. Furthermore, the model revealed that Rot and SarS act synergistically to stimulate spa expression, something that was not obvious from experimental data. We believe that this mathematical model can be used to evaluate the significance of other putative interactions in the regulatory network governing spa transcription.
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| 6. |
- Karlsson, Diana, et al.
(författare)
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Modeling the regulation of the competence-evoking quorum sensing network in Streptococcus pneumoniae
- 2007
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Ingår i: Biosystems (Amsterdam. Print). - : Elsevier. - 0303-2647 .- 1872-8324. ; 90:1, s. 211-223
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Tidskriftsartikel (refereegranskat)abstract
- Competence for genetic transformation seems to play a fundamental role in the biology of Streptococcus pneumoniae and is believed to account for serotype switching, evolution of virulence factors, and rapid emergence of antibiotic resistance. The initiation of competence is regulated by the quorum sensing system referred as the ComABCDE pathway. Experimental studies reveal that competence is down-regulated a short time after its induction and several hypotheses about the mechanism(s) responsible for this shut-down have been presented. Possibly, a ComX-dependent gene product, such as a repressor or a phosphatase, is involved. To better understand the down-regulation of the competence-evoking system in S. pneumoniae, a mathematical model was set up. By analyzing the model, we suggest that shut-down of competence possibly occurs at the transcriptional level on the comCDE operon. As a result of introducing a putative comX-dependent repressor, which inhibits expression of comCDE and comX, in the mathematical model, competence is demonstrated to appear in waves. This is supported by experimental studies showing the appearance of successive competence cycles in pneumococcal batch cultures.
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| 7. |
- Mårdberg, Peter, et al.
(författare)
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Using a formal high-level language and an automated manikin to automatically generate assembly instructions
- 2014
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Ingår i: International Journal of Human Factors Modelling and Simulation. - : InderScience Publishers. - 1742-5549. ; 4:3, s. 233-249
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an approach to automatically generate predetermined motion time system (PMTS) based assembly instruction lists from simulations within digital human modelling (DHM) software. A formal high-level instruction language is used to instruct an automated manikin to perform assembly operations. The manikin, the language and the assembled objects are composed into a discrete model. In a post-computational step, the model is used to construct PMTS instruction lists by mapping the manikin motions, assembled objects and the language instructions onto a set of PMTS keywords. The described approach is implemented in the DHM software IMMA and tested on industrial cases of manual assembly in the automotive industry.
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